In drilling boreholes for emplacement of measurement or sampling devices, the common practice is to install the desired device in the borehole and then to seal the entire hole with a sealing material. U.S. Pat. No. 5,176,207, issued Jan. 5, 1993, to Keller, teaches the use of a flexible tubular member to both seal and support a borehole and to carry instruments into a borehole as the flexible member is everted into the borehole. Instrumentation and sampling devices can then be placed directly in contact with the surrounding structure. These everting liners may be installed from the interior of a pressure canister into the hole or otherwise everted into a borehole or other cavity.
An alternative to drilling single wells to obtain water samples at several elevations in an aquifer is to install several wells of different depths in one deep hole (called nested wells). However, the sealing of a bundle of well casings is difficult. Hence vertical flow in the interstitial spaces in the nested well bundle can prevent the isolation required for the several wells. This problem of a vertical seal of several wells in one hole is especially evident when installing several wells in a very slender, economical borehole.
The present invention allows the emplacement of several wells in a borehole that is sealed, not by a fill material poured around the wells, but rather, with a pressurized flexible liner surrounding the wells. System components are available as needed for repair or replacement. The hole remains open and available for other purposes.
When flexible liners are everted into boreholes, and the like, any instrumentation and sampling tubing attached to the liner must evert with the liner. The instrumentation and tubing will then have to conform to the radius of curvature of the liner at the bottom end of the everting liner. In a small diameter borehole, this radius of curvature will be quite small and can limit the use of such instrumentation and sampling tubing. Accordingly, it is an object of this invention to permit the use of everting liners for sampling and instrumentation in small diameter boreholes.
Various objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.